Why can't humans grow and replace teeth infinitely like sharks?

From babbling to chewing food, teeth are important companions who accompany us as we grow up. We all know that people have two sets of teeth in their lifetime: deciduous teeth and permanent teeth. When it comes to the permanent teeth stage, after the permanent teeth grow and replace, it is really troublesome to have bad teeth. Why can't we have 6 sets of teeth like elephants, or simply evolve the magical ability of unlimited tooth growth and replacement like sharks? Today is National Love Teeth Day, an important day to remind us to pay attention to oral health. How important are teeth? Let's find out.

01 Why do humans have only two sets of teeth?

In fact, we humans also have genes in our DNA that allow us to replace teeth endlessly like sharks, but the expression of this gene is suppressed. Unlike shark teeth, human teeth have different shapes and functions, which can help humans chew a variety of different foods. Most importantly, human teeth need to be aligned and have a reasonable occlusion relationship in order to be convenient to use and function.

It is worth mentioning that the teeth of ancient human ancestors were very sharp and hard, which can be seen from tooth fossils. According to science, modern people eat too soft and delicate food and too much carbohydrates, so our teeth have become weaker than those of our ancient ancestors.

02 Incisors, canines, and molars, what are their respective responsibilities?

From babbling to chewing food, the role of teeth in accompanying us throughout our lives cannot be underestimated. Incisors, canines and molars are different types of teeth in the mouth. They each have different functions and work together to complete tasks such as chewing, pronunciation and maintaining facial shape.

Incisors, which are the shovel-like front teeth, can cut food; sharp canines help tear food, allowing the grinding-like molars to grind food more conveniently. In addition to eating, our teeth also help with pronunciation, such as labiodental sounds. Otherwise, try to pronounce the Chinese pinyin "f" without teeth. Healthy teeth make people look beautiful, eat delicious food, and smile often, which has a great effect on people's physical and mental health.

03 Hardware is not enough, software can make up for it: How to take comprehensive care of your teeth?

Human teeth seem indestructible, but they cannot be lost or replaced, and they have to face various "sneak attacks" from bacteria. But don't worry, here are some good ways to help protect your teeth.

(1) Adjust your diet . Eat more healthy foods such as fresh vegetables and fruits, milk, and meat, and eat less sugary foods and acidic drinks. Also, control the amount and frequency of intake. Eat less sweet, sticky, and sour foods, especially avoid snacking before bedtime.

(2) Brush your teeth regularly . Brushing your teeth is the best way to remove dental plaque. The mechanical friction of a toothbrush combined with the abrasives, detergents and possible functional ingredients in toothpaste can effectively remove dental plaque from the tooth surface and between teeth. Adults are recommended to use the horizontal vibrating brushing method to brush their teeth. Use fluoride toothpaste to brush your teeth every morning and evening. If you wear removable dentures, you should take them out and brush them after each meal. Rinse your mouth in time after meals, snacks and beverages to remove food residues in your mouth.

Although brushing teeth is important, it is not a panacea . Some hard-to-reach gaps or hidden areas between teeth, such as the adjacent surfaces of teeth and gingival sulci, may be difficult to completely clean simply by brushing teeth. Therefore, in addition to brushing teeth, it is also necessary to use auxiliary tools such as dental floss, interdental brushes, and water flossers, as well as regular oral examinations and teeth cleaning.

Don't forget that although deciduous teeth can only accompany us for a part of the journey, they must also be carefully protected. Compared with permanent teeth, deciduous teeth are less calcified and more prone to tooth decay . The worst thing is that once the enamel is damaged, it cannot recover on its own, and there is very little that dentists can do. In our country, more than two-thirds of 5-year-old children have tooth decay, and about one-third of 12-year-old teenagers have tooth decay. In fact, before the baby's teeth erupt, parents can use soft gauze to clean the baby's mouth. After the first deciduous tooth erupts in infants and young children, parents can help the children brush their teeth with a fingertip toothbrush! It is recommended that children use the circular brushing method with fluoride toothpaste to brush their teeth. When two adjacent teeth erupt, dental floss needs to be used to clean the adjacent surfaces of the teeth.

(3) Have regular dental "physical examinations" and seek medical attention if you find any dental problems. Caries, periodontal disease, tooth sensitivity, broken or fallen teeth, etc., if not treated in time, may gradually worsen and lead to more serious consequences, such as tooth loss, oral infection, pain and discomfort, and affect chewing, pronunciation and facial appearance. Don't think that teeth will fall out when you get old. The World Health Organization believes that an 80-year-old should have at least 20 functional teeth. In other words, most teeth can accompany you throughout your life as long as you take good care of them.

It is recommended that dental problems be treated in their early stages, as treatment is often more effective, simpler and quicker. This helps prevent problems from becoming more serious and reduces the complexity and cost of subsequent treatment.

I hope everyone can have good teeth and smile often!

References

1. Willis, JR; Gabaldón, T. The Human Oral Microbiome in Health and Disease: From Sequences to Ecosystems. Microorganisms 2020

2.Uzel, Naciye G., et al. "Microbial shifts during dental biofilm re-development in the absence of oral hygiene in periodontal health and disease." Journal of Clinical Periodontology , 2011

3. The Testimony of Teeth, by Tanya M. Smith, translated by Cheng Sunxuezi, CITIC Press

4. Zheng Xin, Cheng Lei, Zhou Xuedong, Frontiers and progress in dental caries research, Chinese Journal of Stomatology, 2024

5. Professor Joerg Meyle and Professor Norbert Krämer from the University of Giessen, Germany, "Periodontitis and cancer: the role of periodontal etiology", Shandong University Summer Course, 2021

Author: Member of the China Science Writers Association

Reviewer: Si Yan, researcher of the Chinese Stomatological Association, chief physician of Peking University School of Stomatology